Medical science has long recognized the value of drug delivery devices comprising a drug and an erodible polymer. These devices are valuable because the erodible polymer blended with an effective amount of a beneficial drug, erodes at a rate controlled by the inherent chemistry of the polymer itself. Therefore, the device, delivers the drug at a controlled rate and in an effective amount, to a biological environment of use. A major advance towards satisfying this recognition was met by the novel poly(orthoesters) and poly (orthocarbonates) disclosed in U.S. Pat. No. 4,180,646 issued to patentees Nam S. Choi and Jorge Heller. The patent discloses a unique class of polymers comprising a polymeric backbone having a repeating monomeric unit consisting of a hydrocarbon radical and a symmetrical dioxycarbon unit with a multiplicity of organic groups bonded thereto. These polymers reproducably erode in an aqueous or a biological fluid environment to innocuous products. The polymers are useful for delivering a beneficial agent at a controlled rate to the environment of use.
While the above polymers are outstanding and represent a pioneer advancement in the polymer and the drug delivery arts, and while they are useful for delivering numerous beneficial drugs to the environment of use, there is an occasional instance when it is desirable to modify the rate of erosion of the polymer to produce a more preferred dose rate of drug. For example, when the polymers are used in the form of implants in an animal environment of use, it may be therapeutically desirable to modify the rate of erosion of the polymer to achieve any one of a number of dose rates. The dose rates are adjusted by regulating the amount of drug released per unit time by the implant, which is controlled by the rate of polymer erosion. Controlling the release rate is also useful for extending the period of time the implant remains in the environment. It will be appreciated by those versed in the present arts, and in view of this presentation, that if an erosion rate modifier were made available for modifying the rate of erosion of the poly(orthoesters) and the poly(orhthocarbonates), such a modifier would represent a valuable contribution and a useful improvement in the polymer and deliverying arts.